Defensive publication



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DEFENSIVE PUBLICATION UNITED STATES PATENT OFFICE Published at therequest of the applicant or owner in accordance with the Notice of Apr.11, 1968, 849 0.G. 1221. Identification is by serial number oi. theapplication and the heading indicates the number of pages ofspecification, including claims, and of sheets of drawing contained inthe application as originally filed. The file of this application isavailable to the public for inspection; reproduction may be purchasedfor 30 cents per sheet.

Applications published under the Defensive Publication Program have notbeen examined as to the merits of alleged invention. The Patent Oflicemakes no assertion as to the novelty of the disclosed subject matter.

PUBLISHED JULY 15, 1969 735 175 POLYUREA BONDED SAND FOUNDRY CORESMartin Luther Brown, Elkton, Md., and Ward Jepson Remington, WestChester, Pa., assignors to E. I. du

Pont de Nemours and Company, Wilmington, Del., a

corporation of Delaware Filed June 7, 1968. Published July 15, 1969 Int.Cl. C08g 51/04; B29c 1/06 U.S. Cl. 260-37 No Drawing. 15 PagesSpecification A process for the preparation of foundry sand cores whichallows adequate working time but does not require the usual baking step.The cores are prepared by mixing foundry sand with ingredients whichform a polyurea binder resin within the mass in a reasonable time atordinary temperatures, shaping the mix and allowing it to set. Thepolyurea binder ingredients are (1) a solution of an aromaticpolyisocyanate in a non-protonating solvent (described in U.S. Patent3,317,481) suflicient to provide 0.075l.2 parts by weight of isocyanategroups per 100 parts of sand, (2) a source of water at least sufiicientto convert the isocyanates to ureas, preferably an inorganic salthydrate such as trisodium phosphate dodecahydrate and (3) a catalyst forthe isocyanate water reaction such as tertiary aliphatic amines andorganotin compounds. The preferred aromatic polyisocyanates have afunctionality greater than two and can be condensation products ofaromatic diisocyanates with polyols such as trimethylol propane orglycerol or phosgenation products of polyamine mixtures such as thecrude condensation products of formaldehyde and aniline (see U.S. Patent2,683,730). The cores have excellent properties, attaining a scratchhardness of 60 or more in 30-600 minutes at ambient temperatures with aslittle as 0.75 part of binder mixture per 100 parts of sand.

